1. Field of the Invention
The present invention relates to an examination method for cavities under paved roads. The method of the present invention can examine cavities under paved roads such as an asphalt-paved road, a concrete-paved road and an airport runway effectively and precisely.
2. Description of Related Art
Recently, subsidences of roads often occur in urban areas. Accidents caused by the subsidence are reported to responsible parties which has resulted in the recognition of the necessity of investigating for the presence of a cavity or cavities under the paved road.
However, it is not realistic to dig up all paved roads of an extensive distance for investigating underground conditions thereof, from the viewpoint of time, expenditure and traffic.
By using nondestructive cavity examination means based on an electromagnetic wave examination method, it is possible to investigate road structures without large-scale construction such as digging up of the road.
However, it is not practical, judging from examination speed, to use a pushcart type electromagnetic wave underground radar means of the conventional type. In addition, it is difficult to confirm the place detected from the results of the investigation due to troubles such as collapse of the ground caused by vibrations generated by a drive source for the cutting operation specified in the confirmation method.